Alloy piston



Dec. 27, 1932. C R BUTLER 1,891,914

ALLOY PISTON Filed March 13, 1929 s sheets-Sheet 1 Z* 1' Z .2. 45 I? 12a .55 fa Dec.27,1932. R BUTLER gL89L914 ALLOY PI. STON Filed March 15,1929 6 sheets-sheet 2 Dec. 27, 1932. c, R. BUTLER 11,891,914

ALLOY PIsToN Filed March 13. 1929 6 Sheets-Sheet 5 Dc; 27, 1932. c. R.BUTLER 1,891,914

ALLOY PISTON Filed March 15. 1929 6 Sheets-Sheet 4 111.?. 16 L ITI' Z iZi A mbe/"64.1"

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attorney@ Dc. 27, 1932. C, R, BUTLER 1,891,914

ALLOY P I S TON Filed March 1s, 1929 6 Sheets-Sheet 5 155522. i y1715"?3' 2z d ,er ,l il

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ALLOY PIsToN Filed March 15. 1929 6 Sheets-Sheet 6 Il?. 2.9. fa d(5H/6255 /Q 5ans@ Patented Dec. 27, 1932 PATENT OFFICE CHARLES R.BUTLER, OF INDIANAPQLIS, INDIANA Application led March 13,-1929. SerialNo. 346,517.

My invention relates to light-metal pistons for internal combustionengines, with an effective expansion control of such pistons.

It is the object of my invention to make a sturdy light-weight piston,as of aluminum alloy or other light-weight metal having a largeco-eilicient of thermal expansion, with substantially fullcircumferential skirt-bearing at least in the zone between the pistonpinbosses andthe piston-ring belt and desirably also at or near the openend of the piston, and to produce an effective control of the expansionand contraction of the piston skirt, especially in that zone, so that itis more nearly equal to that of iron or' steel; to reduce the internalstresses in the piston due to changes in temperature; towree from thepiston-pin bosses the controlled skirt portions d1rectly over suchbosses, so that there may be relative movement between such portions andthe bosses Without the production of excessive bending stresses; toprovide good heat conductivity between various parts of the piston sothat the heat may be conducted away from the piston head even though notdirectly to the controlled zone of the piston skirt lyingbetween thepiston-pin bosses and f the piston-ring belt; to provide for adequatetransfer of heat from the piston to the cylinder; to reduce pounding andbreakage, by so controlling the expansion and contraction of the pistonthat it fits closely within the cylinder at all temperaturesl throughsubstantially the entire circumference in the zone between thepiston-pin bosses and the piston-ring belt; to provide effective sealingagainst leakage of gas or oil, while yet,` permitting good lubrication;and to accomplish these results in a piston low in manufacturing costand amply rugged to withstand the terrific loads to which pistons ofheavy duty engines are subjected..

In carrying outmy invention, I desirably make the piston as a whole oflight metal, such as aluminum or aluminum alloy, and separate the headand piston-ring belt from the lower skirt portion or guiding'portion bya circumferential slot so that stresses'l willl not be transmitted fromone to the other at or near the periphery of the p'ston;andpro videcarrying struts which connect the piston-pin bosses to the piston head,desirably at points on the latter fairly remote from the peripherythereof; and carry the skirt or guiding portion of the piston from thepistonpin bosses; and provide one or more endless steel bands, which arelocated in the piston skirt or guiding portion below suchcircumferential slot and at least one of which is located between saidslot and the transverse plane of the piston-pin bosses; and slitlongitudinall the light-metal portions of the skirt above tliepiston-pin bosses, and desirably at or nearv the longitudinal plane ofsuch bosses, while permitting the endless steel band e5 or bands tocross said longitudinal slits and complete'the mechanical continuity ofthe skirt; and separate from the piston-pin bosses theskirt portions inthe neighborhood of the aforesaid longitudinal slits s0 that those skirt7o portions may serve as guides without material distortion from thepiston-pin bosses; and in some forms of my invention provide otherlongitudinally extending breaks in the lightmetal portion of the pistonskirt from the open end thereof up to or beyond the pistonpin bosses, oreven to the said circumferential slot,- but desirably at locationsangularly spaced from theflongitudinal plane of the piston pin.

The accompanying drawings illustrate my invention, and show six of themany forms it may take. One form is shown on Sheet 1, Figs. 1 to'5inclusive; another form on Sheet 2. Figs. 6 to 10 inclusive; a thirdform on 85 Sheet 3, Figs. 11 to 15 inclusive; a fourth form on Sheet 4,Figs. 16 to 21 inclusive; a fifth form on Sheet 5, Figs. 22 to 27inelusive; a sixth form on Sheet 6, Figs. 28 to 31 inclusive; and amodification of the Vferroust metal control members also on 32 and 33.

In these drawings, Fig. 1 is a longitudinal section through one type ofpiston embodying my invention, the section being taken on the line 1-1of Figs. 2, 3, and 4, in the longitudinal plane of the piston pin; Fig.2 isa section on the line 2f-2 of Fig. 1, and also substantially on thelines 2-2 of Figs. l3 and 5; Fig. 3 is a transverse section sub- 100sheet 6, Figs.

stantially on the lines 3-3 of Figs. 1 and 2; Fig. 4 is an elevation ofthe piston of Figs. 1 and 2, viewed in the same position as Fig. 2; andFig. 5 is a transverse section substantially on the line 5-5 of Figs. 1and 2: Figs. 6, 7, 8, 9, and 10 are views corresponding generally toFigs. 1, 2, 3, 4, and 5 respectively, but of a somewhat differentspecific embodiment of my invention, the sections on which Figs. 6,7, 8,.and 10 are taken being indicated by the lines 6 6, 7--7, 8 8, and 10-10on others of those figures; Figs. 11 to 15 inclusive are also viewsgenerally correspondirig to Figs. 1 to 5 inclusive respectively, but ofa third specific form of my invention, the sections on which Figs.11,12, 13,

and 15 are taken being indicated by the lines 11--11, 12-12, 13-13, and15-15 on others of those figures; Figs. 16, 17, 19, and 2 0 are viewsgenerally corresponding to Figs. 1, 2 and 4, 3, and 5 respectively, butof a fourth specific embodiment of my invention, and Figs. 18 and 21 arean elevation and a bottom view respectively of the same piston, thevarious sections of which Figs. 16. the right half of 17, 19, and 20 aretaken being indicated by the lines 16-16, 17-17, 19-19, kand 20-20 onothers of those figures; Figs. 23, 23, 24, and 26 are viewscorresponding generally to Figs. 1, 2 and 4, 3, and 5 respectively, butof a fifth specific embodiment of'my invention, the sections on whichFigs. 22, the right half of 23, 24, and 26 are taken being indicated bycorrespondingly numbered section lines on the other figures; Fig. 25 isa transverse section on the line 25-25 of Figure 23; and Fig. 27 is aperspective view of a steel strut which is shown by way of example inthis fifth embodiment of my invention; Figs. 28, 29, 30, and 31 areviews corresponding generally to Figs. 22, 23, 24, and 27, but showing asixth embodiment of my invention, the sections of which Figs. 28, 29,and 30 are taken being indicated by correspondingly numbered sectionlines on others of those figures: and Figs. 32 and 33 are viewscorresponding generally to Figs. 29 and 30 respectively,`but with a pairof overlapping arcuate strips each Ianchored at its end instead of thecontinuous control bands of the other figures.

In all these forms of my piston. thereis a piston head 2O having adepending pistonring-belt 21 provided with piston-ring grooves 22 forthe usual piston rings; pistonpin bosses 23 which are located below thepiston head and its ringbclt,`and which. co-operate with the usualpiston pin, either directly or with suitable interposed bushings 24,such bushings being shown in the first form of my invention.(Figs. 1 to5) by way of example.'

although they may be used or omitted with any form of my invention;carrying struts 25 which extend from the piston-pin bosses at or neartheir inner ends to the head 20, desirably to join the latter in regionsspaced inward from the periphery of the head and from the ring belt, asin the first three and the preferred forms of my invention, so that suchregions are intermediate regions between the center and the periphery ofthe head, a1- though in some instances these struts or webs may alsoextend to and join the ring belt, as in the remaining forms which I haveillustrated of my invention; and a guiding or in weight and has certaindesirable bearingmctal and heat-conducting characteristics. In addition,all the parts 20, 21, 23, 25, and 26 are desirably made as a singlehomogeneous casting, for ruggedness of construction and for highheat-conducting capacity.

The carrying struts 25 from the two piston-pin bosses to the head may beentirely separate from eachother, as for instance in the forms of myinvention shown in Figs. 6 to 15 inclusive; but for heavy work I preferto interconnect them by a pair of webs 27 which extend from the h eaddownward toward the piston-pin bosses in planes'transverse to the struts25, as shown in Figs. 1 to 5, so that the struts 25 and Webs 27 togetherform a box-strut. This smakes for great strength and ruggedness, and isespecially desirable for pistons in heavy duty engines.

In all forms of my invention, the upper edge of the skirt or guidingortion 26 is separated yfrom the lower end o? the ring-belt 21 by acircumferential groove or slot 30; which may be either cut straight in,as for in- IOLl stance in Figs. l to`5 inclusive, or cut in conically,as in Figs. 6 to'15 inclusive, and which if desired may communieatewithone of Vthe piston-ringgrooves 22 usually the lowest one,

as in Figs. 1 to 5 inclusive, or may be slightly i substantiallyparallel to each other, and to the pistonjaxis, as ,in the form ofpiston shown in Figs; 1 to 5 inclusive; or they may be inclined withrespect to each other an/d to the piston axis.l as inthe forms of myinvention shown in Figs. 6 to 10 and 11 to 15. These struts join thepiston-pin bosses at or fairly near the inner ends of the latter, sothat the struts are spaced inward from that portion of the piston skirtwhich liesbetwen the circumferential slot 30 and the piston-pin bosses,to leaye a space 31 between such struts and that portion of the pistonskirt.

The piston skirt 26 may yextend for substantially the fullcirc'umferenceof the7 piston its asseoir' my invention, however, the pislon shirtextends for substantially the compl-eee eircomerence in a zone lyinghetwee the sirens-.1.4 erential slot 30 .end the transverse plane of thepiston-pin boes, save eertsin slits which will shortly describedn Thatis, whether the shirt below the igiene the pis- 'ein bosses extends forthe complete eirr-ence or is merely e peir of siippers, the plane o'ithe esten-pin bosses it ezitends snhstnn'tielly the nli eircnniier ence,for the slits rei-erred to, so that there it 'will iorin -snbstentiellycomplete snide for the piston throughout s cir-enroy renee, not only inthe nien-e of the but else in the longitudinal piene of 'n if 'ion pinso that roeiiingij oi the pis on piston rings Win i will zfiso forni esul here ere ons or i i enioedded in the -nieiei or piston l 1 y slnr'z.Tney are desirelolrly endless steel rings, as molested in eli `orrnsshown of insentieri sere that shown in Figs. 552 end There is least onesneh stesi control band 35 in 'the zone just referred to, between theeireurnerentiai slot 3@ and the transverse piene of the piston-pinbosses. This control band may be ot any suitable cross-section, eitherrectangular or round, as shown in the serions views f the drawings'. Itmay be oiE any suitable iron or steel composition, to control the exansion oi the piston skirt in its plone; so t' at it may be eitherordinary iron or steel, or it may be of some ferrous-metal alioy (suchas a nickel-steel alloy of which inver is one example) which has aoo-eicient oi thermal expansion less than that of cast iron or steel ifin the design of the piston that lower co-ei'cient of thermal expansionis desired, Ordinarily l prefer that this control hand have a greaterco-eicient of thermal expension than has inver, because the co-eii-lcient of thermal ex ansion of invar is ordinarily too small or producingthe best results; but invar may be used if desired. While I have shownonly one ferrous-metal control band in the zone between thecircumerential slot and the piston-pin bosses, as that is suicient toillustrate my invention, such invention is not at 'all limited to theuse of only a single control band in that general location. But myinvention does contemplate the use of atleast one control bend in thatgenerell loeetion, 'whether or not more thonone control hand is used inthat location, and Whether or not a control band or bends ore else usedin other locations now to he described.

Tous in .addition to a control hand in the zone just described, theremay be one or :more lower control bands 35, also o' suitable ferrousmetal, located in the zone between the transverse plane or" thepiston-pin bosses ond 'the open end of the cylinder. rEhese areesgeeeialiy desirable in the full-skirt type of piston, such es shown inFigs. l to i0 in- 'cinsiveg elthongh not essential to many forms of myinvention, and thus not shown in the forms oi my invention ilnstreted inFigs. li to inclusive. 'lhst is, the lower control bend is `notnecessary to my present invention, :although frequently desirable, loutupper control bend 35 is essential to it. The shirt 26 is carried fromthe piston-pin bosses IThis carrying of the sltirt from *eisten-pinbosses is such that the shirt ons which lie between the transverse onethe piston-pin bosses and the ring,y end the neighborhood othelongitndinei I iene of the bosses, are free from di- .ichnient to suchbosses. To end, the shirt may be attached to the piston-loin bosses invarious ways. it may be directly continuons with the lower portions orthe outer ends o1? the piston-pin bosses 23, es in the 'forms shown inFigs. i to 5 inclusive and 6 to l@ inclnsive; with suitablestrengthening webs interconnecting it to the bosses at and below theplane of the piston-pin axis ir desired; such sstronsverse Webs 40 whichextend from the piston-pin bosses ont to the shirt as illustrated inFig. 2, 3, and d and lie slightly below the transverse plane o thepiston pin, or transverse webs 4l and oblique webs 42 which lie in andbelow such trans; verse plane as illustrated in Figs. 7, 8, and l0.These constructions are suitable or the full-skirt type of piston. Ifthe skirt is of the slipper type below the transverse plane of thepiston pin, it may be supported from the bosses by transverse carrylngWebs i3 which lie wholly or at least largely below the transverse planeof the piston-pinaxis, Y

as is illustrated in Figs. l1 to 15. The webs 43 are symmetrical withrespect to the longitudinal plane of the piston pin. lf desired,however, there may be such webs 43* and 43 which are unsymmetrical withrespect to such plane, as is illustrated in Figs. l? and 20, the webs 43extendin from the open end of the piston up to and yond the' transverseplane of the piston pin, While the webs 43 do not extend so high. Thewebs 43* join the bosses to the thrust face which takes the side thrust`on the explosion stroke of the engine, and are made to extend higherthan do the webs 43" so that they may be better able to do so. In thearrangement shown in ranged, as in all the forms of my invention Figs.22 to 33, the webs 44 which interconnect the skirt segments to thepiston-pin bosses do not extend so high as the vaxis of such bosses,save where they join such bosses on the underside thereof.

In any case, the portion of the skirt 26 in the zone between thecircumferential slot 30 and the transverse plane of the piston pinextends for substantially the entire circumference, has embedded in it acontrol band 35, and in the regions which lie over or `near the ends ofsuch bosses is free from direct attachment to the bosses so that somerelative movement between those' regions and the bosses is permitted.

The skirt portion which lies in this zone is provided with slits 45,which extend longitudinally of the piston and which are crossed by thecontrol band 35 to complete the mechanical circumferential continuity ofthe skirt'structure in spite of those slits. These slits 45 are thusonly in the alulninum. Usually, and desirably, the slits 45 are locateddirectly above the ends of the piston-pin bosses, as shown in all theforms illustrated of my invention save that in Figs. 16 to 21 inclusive;but in that form they are shown as angularly shifted from that locationtoward each other on one side of the longitudinal plane of the pistonpin, usually but not always the side opposite that which is the thrustside of the explosion stroke. I prefer the symmetrical arrangement shownin the other figures, with the slits 45 substantially in thelongitudinal plane of the piston-pin axis; but the nnsymmetricalarrangement shown in Figs. 16 to 21 inclusive, especially if combinedwith the unsymmetrical arrangement of the webs 43 and 43", has certainadvantages, especially when the side thrust is heavy.

By reason of the slits 45, the skirt portion above the region aroundeach end of the piston pin comprises one or two aluminum fingers 46. lfthe slits 45 are symmetrically arshown except that in Figs. 16 to 21inclusive, there are two such fingers 46, which project toward eachother substantially free from any immediate connection to the piston-pinbosses: and these fingers are joined, and the gap between them spanned,by the endless steel control band 35 which extends completely around thepiston and in doing so projects from the end of each projecting finger46 across the intervening gap formed by the slit 45 and into the finger46 on the other side of such gap. lf' the slits 45 are arrangedunsynunetrically. as in the arrangement shown in Figs. 16 to 21, theremay be only one such finger 46 over each piston-pin boss, which fingerextends from the thrust face on one side (the left as shown in Fig. 17)over the piston-pin boss to the slit 45, here shown arranged at the edgeof the thrust `face on the otller side (the right side as shown in Fig.1

The finger or fingers 46 may lie directly over the outer ends ofthepiston-pin bosses, as in the second, third, fourth, fifth, and sixthforms of my invention, shown in Figs. 6 to 33 inclusive, in which casethere may be a fairly wide slot 47 open to the outside of the pistonskirt between the upper portion of the outer end of-each pistonin bossand the lower edges of the finger or ngers 46. This slot iscrescent-shaped in the second and third forms of my invention, shown inFigs. 6 to 15 inclusive, in the third form of my invention extendingdownward to -form the side edges of the lower parts of the thrust facesofthe piston skirt. In the fourth form of my invention, shown in Figs.16 to 21 inclusive, such sloti47 is like that in the third form on theside toward one thrust face, usually the one which takes the thrust onthe explosion stroke, though on the other side the upper edge of theslot extends horizontally alongthe under side ofthe finger 46 to theslit 45. In the fifth and sixth forms of my invention, shown in Figs. 22to 33 inclusive, thefingers 46 are shown flat on their under sides, andspring only from the topmost parts of the .thrust portions of the skirt;so that the slot 47 between the bosses 23 and such fingers 46 isapparently not in the shape of a crescent, although effectively it isstill crescent-shaped. Thus in all of these forms of my invention, thereis in effect a crescent-shaped separation 4T which separates the outerends of the bosses 23 from the finger or fingers 46 which overlie suchouter ends.

However, especially if the length of the piston is limited, the fingers46 may lie radially outward beyond the outer ends of the upper parts ofthe piston-pin bosses, and at about the same height as such upper parts,instead of directly overlying the bosses. This is the situation in theform of my invention shown in Figs. 1 to 5 inclusive. In this case, thefingers 46, which lie radially beyond the outer ends of the upperortions of the pistonpin bosses, are separat from such upper portions ofsuch outer ends by vertically extending slots 48, which lie just insideof the fingers 46. The slots 48 have the same general function as thegenerally crescent-shaped slots 47. It is usually in such cases as thisthat I may provide the bushings 24, although they are not necessary evenhere, so that if they are provided the slot 48 may not extend completelyto the bearing surface of the piston pin. Any relative movement betweenthe fingers 46 and the piston-pin bosses 23 in this construction will beby relative movement of the fingers toward and from the ends of thebosses. or along the bushings 24 if they are provided. To facilitatethis, a slight clearance may be provided around the outer ends of thebushings 24, although only a microwave slots 50 in the moldingoperation, and also the slits 45 and slots 47 but usually form thecircumferential slot 30 by a machining operation subsequent to molding.

In operation, heat which is produced in the piston head by theexplosions is transmitted by the carrying struts 25 to the piston-pinbosses, and thence to the piston skirt, whence it may be dissipated tothe cylinder and the cooling water.

In this operation, there are different rises in temperature in thedifferent parts of the piston. The piston head naturally gets thehottest. This produces expansion, which is substantially the same in alldirections, and

which is an expansion with the co-eliicient of thermal expansion ofl thealuminum or aluminum alloy or other light metal used. The expansion ofthe head as it is heated causes the carrying struts 25 to be separatedsomewhat, thus tending to carry the piston-pin bosses 23 slightlyradially outward. The amount of such separation of the bosses 23 dependsupon a number of factors, notably on the deflection of such struts andthe distance they are spaced apart where they join the piston head. Theuse of the webs 27 tends to prevent such deflection of the struts 25, byreason of the strength of the box-strut which the carrying struts 25 andthe webs 27 together form. The closer together the upper ends of thecarrying struts 25 are placed, the less the forcing apart of thepiston-pin bosses will be by reason of the expansion of the head;because of the reduction in the intervening distance between them at thehead where aluminum-expansion mainly occurs.

The separation of the bosses 23 is also opposed by the upper controlband 35, and by the lower control band 36 if it is present. However, theupper control band 35 permits some such expansion, for the piston-pinbosses may move outward slightly, while the tingers 46 do not moveoutward so far, if at all, .on account of the fact that the fingers 46are free from direct attachment to the piston-pin bosses and are held bythe steel control band 35 from moving out more than that control bandpermits. In consequence, as the piston increases in temperature, boththe space 31 and the slits 45 tend to narrow somewhat, as indeed do theslots 50 also ,When the lower control band 36 is used.

The narrowingV of the slits 45 and of the slots 50 is due to thediierential expansion of the control bands 35 and 36 on the one hand andthe aluminum alloy directly embedding them on the other hand, suchcontrol bands serving as tracks on which the aluminum slidescircumferentially in such differential expansion. The narrowing of thespace 31 is due to the restraint against outward expansion exercised bythe control band 35 on the vfingers 46 as the piston-pin bosses 23 areforced apart by the expansion of the head. Such relative movement ispermitted by the fact that the fingers 46 and the upper portions of thebosses 23 are separate from each other, so that any bending which may beincident to such narrowing of the space 3l is so slight that it is notdetrimental.

Because of these interactions of parts, the fingers 46 co-operate withthe rest of the piston skirt to form an effective cross-head to guidethe piston smoothly. The fingers 46 serve as firm supports for thepiston in the neighborhood just above the regions at the end of thepiston pin, for they are located between the ring-belt and thepiston-pin axis where they are most effective in doing this. Thesefingers 46 eHectually prevent chattering of the piston againstthecylinder wall in the line of the piston pin, and thereby reduce thewear on the piston rings and on the head section, and serve to hold thehead section properly in place.

I claim as my invention:

l. A composite piston, comprising a piston head and piston-ring belt,piston-pin bosses, carrying struts interconnecting said head and saidpiston-pin bosses, a piston skirt carried from said piston-pin bosses,said skirt having portions which lextend and lie between the bosses andthe head, and which fill substantially the entire space between saidparts, and which portions are spaced from said carrying struts and arefree from direct attachment to the upper sides of the piston-pin bossesand are provided with slits extending lengthwise of the piston, and acircumferentially extending control bandof differentmetal from theaforesaid parts of the piston and embedded in the metal of the skirtbetween the ring belt and the transverse plane of the piston-pin axisand extending across said slits, said ring belt and said skirt beingseparated by a circumferential slot.

2. A composite piston, comprising a head having a depending piston-ringbelt, pistonpin bosses, carrying struts interconnecting said head andsaid'piston-pin bosses and joining the latter neartheir inner ends, askirt having thrust portions supported from said piston-pin bosses,saidthrust portions havin projecting fingers vextending circum'feretially of the piston in between and substantially filling the spacesbetween-said pistonring belt and the upper parts of the pistonpinbosses, each finger extending toward and almost but not quite to acooperating finger projecting from the other thrust portion so that agap is left between each two fingers which project toward each other,said fingers lying in the transverse plane of the piston between thering belt and the piston-pin axis and being free from direct attachmentto the` upper parts of the piston-pin bosses, and a circumferentiallyexterding control band of different metal from the skirt and fingers butembedded therein and spanning said gaps between the adjacent ends of thefingers, said ring belt and said skirt and fingers being separated by acircumferential slot.

3. A composite piston, comprising a' head 5 having a dependingpiston-ring belt, pistonpin bosses, carrying struts interconnecting saidhead and said piston-pin bosses, a skirt having thrust portionssupported from said piston-pin bosses, said thrust portions havingprojecting fingers extending circumferentially of the piston in betweenand substantially filling the spaces bftween said pistonring belt andthe upper parts of the pistonpin bosses, each finger extending` towardand 15 almost but not quite to a cooperating finger projecting from theother thrust portion so that a gap is left between each two fingerswhich project toward each other, said fingers lying in the transverseplane of the piston be- 29 tween the ring belt and the piston-pin axisand being free from direct attachment to the upper parts of thepiston-pin bosses, and a circumferentially extending control band ofdifferent metal from the skirt and fingers 25 but embedded therein andspanning said gaps between the adjacent ends of the fingers, said ringbelt and said skirt and fingers being separated by a circumferentialslot.

In witness whereof, I have hereunto set my 30 hand at Indianapolis,Indiana, this 9th day of March, A. D. one thousand nine hundred andtwenty-nine.

CHARLES R. BUTLER.

